It is known that a tantalum pentoxide film with a dielectric constant of several tens has been adopted to achieve a high degree of integration of a semiconductor device, in lieu of a silicon oxide film (dielectric constant: about 4) and a silicon nitride film (dielectric constant: about 7) which have been used for a capacitor dielectric (for example, refer to patent document 1).
There is a method to produce a capacitor comprising a tantalum pentoxide film, wherein the tantalum pentoxide film is formed on the capacitor's bottom electrode, the film crystallized by heat-treatment, and then the capacitor's top electrode formed thereon. The reason for heat-treating the tantalum pentoxide film is to obtain a capacitor with higher electric capacitance using a characteristic of the tantalum pentoxide film in which crystallization provides a higher dielectric constant. However, in this manufacturing process, it is known that a heat-treatment at a temperature higher than 750° C. is necessary to fully crystallize the tantalum pentoxide film (for example, refer to patent document 2).
Hereinafter, the heat-treatment temperature used for crystallizing the dielectric is called a crystallization heat-treatment temperature.